Electron discharge device



'M 7, 1939- H. IG. LuBzYNsKi E T. AL

ELECTRON DISCHARGE DEVICE Filed Jan. 15, 1937 J 6. Fregm -n Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE 9 ELECTRON DISCHARGE DEVICE Hans Gerhard Lubszynski, Hillingdon,

and

England, a company of Great Britain Application January 15, 1937, Serial No. 120,642 In Great Britain January 15, 1936 8 Claims.

This invention relates to electron discharge devices having photo-electrically-active electrodes.

In the manufacture of electron discharge devices comprising anelectrode bearing a deposit of photo-electrically-active material, such as caesium, it is often desirable to prevent or to retard the access of this material to other elements within the envelope of the electron discharge device.

The chief object of the present invention is to provide improved methods of manufacturing such devices whereby the difliculties usually encountered in preventing the deposit of the photo-electrically-active material upon certain electrodes or supports where such deposit is not desired are reduced or avoided, and improved designs of electron discharge devices for use in such methods. 1

According to one feature of the present invention, electron discharge devices are manufactured with a view toavoid j g or reducing the abovementioned dificulties by inserting within the envelope of the device, in addition to the electrode intended to be sensitised with photo-electricallyactive material, an element or material capable of absorbing said photo-electrically-active material, shielding said element or material during the photo-sensitising operation and thereafter displacing the shield to expose the whole or a part of said element or material.

Another feature of the invention is the manufacture of an electron discharge device in which excess photo-electrically-active material is ab sorbed, and this feature of the invention comprises the steps of inserting in the envelope of the device an element having on one of its surfaces a material capable of absorbing said photo-sensitive material, shielding said surfa fi, introducing said photo-electrically-active material and thereafter exposing said surface to absorb excess photo-electricallyractive material.

In order that the said invention may be clearly understood and readily carried into effect, the same will now be more fully described with reference to the accompanying diagrammatic drawing in which:

Figure 1 illustrates a light-transformer, the fluorescent screen of which is adapted to be shielded during photo-sensitisation,

Figure 2 illustrates a conventional form of cathode ray tube in which excess photo-electrically-active material is absorbed after photo-sensitisation,

Figure 3 is an end elevation lookingtowards the right-hand end of Figure 2,

Figure 4 is a view similar to Figure 3, but showing a modified and preferred form for absorbing excess photo-electrically-active material,

Figure 5 shows a further form of the invention, and

Figure 6 shows an enlarged detail of a portion of Figures 2 and 5.

Referring to Figure 1 of the drawings, this illustrates a light-transformer, comprising an evacuated envelope 5 having at one end an electrode 6 which is adapted to be photo-sensitised and, at the other end, a fluorescent screen 1. Prior to photo-sensitisation of the electrode 6, a shield 8 is placed in contact with the fluorescent screen I so as to prevent the photo-electricallyactive material, such as caesium, from becoming deposited on the screen I. The shield 8 is made of mica or of other suitable material and consists of a flat plate of such a shape that it is capable of covering the surface of the fluorescent screen. In the example shown, the shield 8 is hinged at the lower end of the screen 1 as indicated at 9, andsuch hinge may be carried by a support I for the screen I. The shield 8 serves to prevent photo-electrically-active material becoming deposited on the fluorescent screen 1 Whilst the screen 6 is being sensitised and after the envelope has been finally evacuated the shield 8 is dis-' placed to the position indicated in, dotted lines so that it will not interfere with the normal operation of the device. The shield 8 may be moved to the dotted line position shown by manipulation of the tube or, alternatively, a clip of magnetic material, such as iron, may be provided on the mica plate so that the shield can be manipulated from the exterior of the envelope by a suitable magnet. In some cases, instead of the shield 8 being hinged, it may be normally unconnected with the screen I or its support, the envelope being maintained in a suitable position during sensitisation so that the shield is maintained in the required position and after the sensitising operation, the envelope is manipulated to displace the shield so as to expose the screen I for normal operation.

The device shown in Figure 1 is, as aforesaid, a light-transformer, but the invention is not limited in its application to light-transformers, since it can also be applied to similar devices, such as one in which the screen 7 is replaced by a mosaic screen.

Figures 2 and 3 of the drawing illustrate the application of the invention to the case in which it is desired to absorb excess-photo-electricallyactive material after the sensitising operation.

The invention is shown as applied to a cathode ray tube comprising a bulbous envelope IIJ having a mosaic screen H in the bulbous portion which is adapted to be sensitised with photoelectrically-active material. The mosaic screen in the example shown, comprises a mica disc having on one face a large number of separate oxidised silver elements and on the other face a continuous silver layer which forms a signal plate. The mosaic screen I! is held in position in the envelope it! by a support plate l2 consisting of a disc of mica extending nearly to the walls of the bulb and supported therein by radial springs H3 at three points as shown in Figure 3. A semi-circular flap of mica or other suitable material M is hingedly attached at its straight edge to the back of the support i2 in such a manner that, when it pivots about its hinge, its curved edge sweeps adjacent to the wall of the bulb. The support plate may be unsilvered, and the mica flap provided with an oxidised silver coating on the side adjacent the support plate. Alternatively, the support plate may have an oxidised silver coating on its back over at least the area of its surface adapted to be covered by the flap, and the flap in this case may or may not be provided with an oxidised silver coating on the side adapted to contact with the silvered part of the support plate. Preferably however the whole of the back of the support plate and both sides of the flap are coated with oxidised silver aggregated into minute sub-divisions. The curved edge of the flap may carry a soft iron clip 55 which enables the flap to be swung round by means of a magnet outside the bulb. During photo-sensitisation of the mosaic screen, the flap lies in contact with the surface of the support plate f2 so that at least a part of the silver coating on one of these members is shielded. After the mosaic screen has been photo-sensitised, the flap is displaced to the dotted line position shown in Figure 2, so as to expose the silver previously shielded, which is now capable of absorbing excess caesium. The flap it may be held during normal operation of the tube in the dotted line position shown in Figure 2, so that the surface which absorbs excess photo-electrically-active material is normally exposed by causing the flap M to jam between the support plate I2 and the wall of the envelope iii.

The arrangement described in connection with Figures 2 and 3 may be modified as shown in Figure 4 by substituting for the flap a pair of discs i6 and I! of mica or other suitable material having approximately the diameter of the support plate l2 and loosely riveted together at their centres at is. The disc i1 is riveted to the back of the support plate, for example, at the points where the three supporting springs it are attached. The other disc l6 which lies on the back of the disc it, is provided with sectorshaped slots 19 uniformly spaced and exposing nearly one-half of the surface of the under disc H, which surface is coated with oxidised silver, which may be aggregated. The outer surface of the slotted disc may also be coated with oxidised silver, which may be aggregated. A soft iron clip 20 is riveted to the edge of the slotted disc and enables this disc to be rotated about the central rivet 58 by means of a magnet, so as to expose, when desired, a fresh surface of silver through the slots.

The arrangement last described has the following advantages. As it operates in a plane parallel to that of the support plate, it is easy to move; it does not tend to buckle the assembly and it effectively prevents diffusion of caesium between the slotted disc and the under disc. Furthermore, the under disc serves to stiffen the mosaic screen as a whole, and the weight is taken directly by the support springs.

In some cases the material on the electrode or other part to be shielded may be impaired due to direct contact of the flap 8 or l4, and to avoid their direct contact the periphery of the flap may be provided with an annular rim which maintains the shield out of contact with the electrode or part to be shielded, the flap and rim effectively obscuring the electrode until the flap is displaced as above described.-

In another form of the invention as shown in Figure 5, for the purpose of absorbing excess photo-electrically-active material, an absorbent, such as cuprous oxide, may be contained in a cupshaped receptacle 25 suitably positioned within the tube on a support such as l2, the absorbent being normally shielded by the provision of a cap 26 fitting over or into the cup-shaped receptacle. When it is desired to expose the absorbent, the cap may be removed by manipulation of the device, or by magnetic means cooperating with a ing said shield to the other side of said support,

a part of said other side of the support being coated with material capable of absorbing photosensitizing material, said shield being adapted to cover the absorbing material during sensitization of the surface and to be pivoted to expose the absorbing material after sensitization.

2. An electron discharge device comprising an envelope, a support member within said envelope a portion of one side of which is coated with material capable of absorbing photo-sensitizing material, a surface to be photo-sensitized, a shield member, means pivotally securing said shield to the coated side of said support, and means securing said surface to the other side of said support, said shield being adapted to cover the absorbing material or to expose the same.

3. An electron discharge device comprising an envelope, a support member within said envelope, a surface to be photo-sensitized, a shield member, means securing said surface to one side of said support, the other side of the support having a portion thereof coated with a material capable of absorbing photo-sensitizing material, and means pivotally securing the shield to said other side of the support whereby the absorbing material may be exposed or covered by the shield by manipulation of the device.

4. An electron discharge device comprising an envelope, a support member within said envelope, a surface to be photo-sensitized, a shield member, means securing said surface to one side of said support, the other side of the support having a portion thereof coated with a material capable of absorbing photo-sensitizing material, means pivotally securing the shield to said other side of the support, and magnetic means attached to said shield whereby the shield may be pivoted to shield member, means securing said surface to one side of said support, means hingedly securing said shield to the other side of said support, the side portion of said shield next to the said other side of the support being coated with material capable of absorbing photo-sensitizing material, said shield being adapted to lie in contact with said support to conceal the absorbing material or to be hinged from said support to expose the absorbing material.

6. An electron discharge device comprising an envelope, a support member within said envelope, a surface to be photo-sensitized, means securing said surface to one side of said support, a shield having one side coated with material capable of absorbing photo-sensitizing material, and means hingedly securing said shield to the other side of said support with the coated side adjacent thereto whereby the absorbing material may be concealed or exposed.

7. An electron discharge device comprising an envelope, a support member within said envelope, at surface to be photo-sensitized, means securing said surface to one side of said support, a shield having one side coated with material cap-able of absorbing photo-sensitizing material, means hingedly securing said shield to the other side of said sup-port with the coated side adjacent thereto, and magnetic means attached to said shield whereby the shield may be hinged to conceal or expose the absorbing material.

8. An electron discharge tube comprising an envelope, a support member within said envelope, a surface to be photo-sensitized, means securing said surface to one side of said support, a circular shield having one or more sector openings therein, corresponding sector shaped portions of the other side of said support being coated with a material capable of absorbing photo-sensitizing material, and means pivotally securing the shield to said other side of the support for angular movement whereby the absorbing material may be covered or exposed.

HANS GERHARD LUBSZYNSKI. GEORGE STANLEY PERCIVAL FREEMAN. 

